Snap-fit plastic fasteners for securing one item or part to another in an assembly are used in many industries for many purposes. Such fasteners are known in a variety of shapes and configurations, and may have snap-fit connections to each component, interlocking engagement to one component, threaded engagement to one component or to a second fastener component and various other attachment configurations.
It is known in automotive applications to have one or more components that are pre-assembled at one location and shipped to another location for assembly with one or more other components. The pre-assembly may include installation of a fastener, such as a bolt and nut. The nut may be attached to the bolt prior to final assembly, requiring that the nut be removed from the bolt during final assembly only to be reattached to the bolt upon final assembly. So called part-in-assembly (PIA) applications wherein the fastener is connected to one part and transported to another location for final assembly in which the part with fastener is installed on the automobile have achieved broad acceptance. However, disassembly of a bolt and nut fastener is time consuming and sometimes problematic in that the removed nut can be dropped or misplaced, requiring that a spare nut be available for use. When a fastener having a nut is used, it is also necessary to keep the end of the fastener exposed for access to the nut until final assembly is completed. In other applications, a pre-assembly may only include a bolt. The nut is later assembled to the bolt during final assembly at the manufacturing plant. The nut increases cost, assembly time and sometimes requires the use of specialized tools.
Various types of deflectable fasteners, so-called“snap-fit” fasteners, have also been used in which one or both ends of the fastener are adapted for inward deflection as the fastener is forced into a hole of a part in which it is installed. The deflectable portion rebounds outwardly after passing through the hole, securing the fastener in the hole of the part. These types of fasteners have advantages in that the fastener is one-piece and can be assembled quickly by merely pushing the fastener into the part or pushing the part onto the fastener. Such fasteners also provide advantages in so-called blind fastening assemblies, wherein the first and second parts overlie each other covering the hole and the fastener, or in other applications there is no access to the inside of the hole or the installed fastener. For example, it is known to use snap-fit PIA assemblies to attach molding to a vehicle body.
A disadvantage of such fasteners is that the fastener can be difficult to remove. In some applications and uses, the retention force requirement is high such that the parts are not easily pulled off the fastener. Accordingly, such fasteners can be designed with relatively easy inward deflection of the components for insertion through a hole but configured such that the part is not easily deflected for extraction. In some situations, the fastener must be broken or otherwise damaged to remove one part from the other. When reapplying automobile trim to an automobile body, for example, it may be necessary to provide all new fasteners if the original fasteners are damaged upon removal of the trim for body repair or other servicing. Replacing the fasteners when reattaching the molding is both inconvenient and expensive. Further, removal is difficult and can be time consuming.
There is a need for a snap-fit fastener that can be pushed into parts for connection without requiring difficult attachment procedures, with the fastener being one piece and having a high extraction force but being removable and reusable.